The present invention relates to an organosilicon compound, to a catalyst for olefin polymer production, and to a method for producing olefin polymers. More precisely, the invention relates to an organosilicon compound having a specific structure, to a catalyst comprising the compound for producing olefin polymers having increased stereospecificity and increased melt fluidity, and to a method for producing such olefin polymers.
As having a high degree of crystallinity, olefin polymers, especially polypropylenes are tough and have good tensile strength, heat resistance, chemical resistance and optical characteristics, and are well workable. In addition, they are more lightweight than polystyrenes, and are much used in the field of injection moldings, containers, wrapping and packaging materials, etc.
However, in order to further broaden the application field of polypropylenes, their toughness and heat resistance that are inferior to those of polystyrenes and ABS resins must be further improved. It is known that olefin polymers having a higher degree of stereospecificity have higher toughness and better heat resistance. Therefore, it is desired to further increase the stereospecificity of olefin polymers.
In general, olefin polymers are produced by the use of Ziegler-Natta catalysts comprising a titanium compound and an organoaluminium compound, for which, therefore, tried are (1) increasing catalyst activity, (2) increasing the stereospecificity of olefin polymers produced, and (3) improving the powdery morphology of olefin polymers for their stable production.
In producing polypropylenes, generally used is a catalyst system that comprises a solid catalyst component composed of titanium, magnesium, chlorine and an electron donor compound, and an organoaluminium compound. It is known that adding an organosilicon compound with Sixe2x80x94Oxe2x80x94C bonds to the catalyst system increases the stereospecificity of the polymers produced. For example, Japanese Patent Laid-Open No. 84404/1990 discloses a catalyst system that comprises a cyclopentylalkyldimethoxysilane, dicyclopentyldimethoxysilane or the like. However, the silicon compound-containing catalyst system disclosed is problematic in that the melt fluidity dependency of the polymers produced on the amount of hydrogen used in their production is low, and therefore a larger amount of hydrogen must be used for producing polymers having increased melt fluidity, which, however, detracts from the productivity of the polymers since the monomer partial pressure shall be low.
On the other hand, Japanese Patent Laid-Open No. 223008/1988 discloses a catalyst system containing di-n-propyldimethoxysilane or the like, in which the silicon compound used increases the melt fluidity dependency of the polymers produced on the amount of hydrogen used in their production. However, the stereospecificity of the polymers produced by the use of the catalyst system is still unsatisfactory, and the polymers are still problematic in that their moldings could not still have a desired degree of toughness. Therefore, for obtaining tough moldings of the polymers, their wall thickness must be increased, for which the amount of the polymers to be used shall increase.
The object of the present invention is to provide a catalyst for olefin polymer production, which is effective for producing olefin polymers having increased stereospecificity and increased melt fluidity, and also to provide a method for producing such olefin polymers.
We, the present inventors have assiduously studied in order to attain the object as above, and, as a result, have found that the problems noted above can be solved by the use of a catalyst for olefin polymer production that comprises a solid catalyst component composed of titanium, magnesium and an electron donor compound, an organoaluminium compound, and a novel organosilicon compound of a general formula (I) mentioned below. On the basis of this finding, we have completed the present invention.
Specifically, the invention provides an organosilicon compound, a catalyst for olefin polymer production, and a method for producing olefin polymers, which are mentioned below.
(1) An organosilicon compound of a general formula (I): 
wherein R1 to R3each represent a hydrogen atom or a hydrocarbon group, and they may be the same or different, and may be bonded to the adjacent group to form a ring; R4 and R5 each represent a hydrocarbon group, and they may be the same or different, and may be bonded to the adjacent group to form a ring; R6 and R7 each represent a linear hydrocarbon group having from 1 to 10 carbon atoms, and they may be the same or different; m is an integer of at least 2; and n is an integer of at least 1.
(2) A catalyst for olefin polymer production, which comprises (A) a solid catalyst component comprising titanium, magnesium and an electron donor compound, (B) an organoaluminium compound, and (C) the organosilicon compound of (1).
(3) A method for producing olefin polymers, which comprises polymerizing an olefin by the use of the olefin polymer production catalyst of (2).
(4) The method for producing olefin polymers of (3), wherein the olefin is propylene.
The organosilicon compound of the invention is a novel compound having the structure of above-mentioned general formula (I). That is, the compound is represented by: 
wherein R1 to R3 each represent a hydrogen atom or a hydrocarbon group, and they may be the same or different, and may be bonded to the adjacent group to form a ring; R4 and R5 each represent a hydrocarbon group, and they may be the same or different, and may be bonded to the adjacent group to form a ring; R6 and R7 each represent a linear hydrocarbon group having from 1 to 10 carbon atoms, and they may be the same or different; m is an integer of at least 2; and n is an integer of at least 1.
Concretely, R1 to R3 include a hydrogen atom; linear hydrocarbon groups such as methyl, ethyl and n-propyl groups; branched hydrocarbon groups such as isopropyl, isobutyl, t-butyl and thexyl groups; saturated cyclic hydrocarbon groups such as cyclobutyl, cyclopentyl and cyclohexyl groups; and unsaturated cyclic hydrocarbon groups such as phenyl and pentamethylphenyl groups. Of those preferred are a hydrogen atom and linear hydrocarbon groups having from 1 to 6 carbon atoms; and especially preferred are a hydrogen atom, and methyl and ethyl groups.
R4 and R5 include linear hydrocarbon groups such as methyl, ethyl and n-propyl groups; branched hydrocarbon groups such as isopropyl, isobutyl, t-butyl and thexyl groups; saturated cyclic hydrocarbon groups such as cyclobutyl, cyclopentyl and cyclohexyl groups; and unsaturated cyclic hydrocarbon groups such as phenyl and pentamethylphenyl groups. These may be the same or different. Of those, preferred are linear hydrocarbon groups having from 1 to 6 carbon atoms; and especially preferred are methyl and ethyl groups.
R6 and R7 include linear alkyl groups such as methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl and n-octyl groups. These may be the same or different. Of those, preferred are linear alkyl groups having 1 or 2 carbon atoms; and especially preferred is a methyl group.
Typical examples of the organosilicon compound of formula (I) are those where R1 to R3 each are a hydrogen atom, or a linear hydrocarbon group having from 1 to 6 carbon atoms, and they may the same or different, and may be bonded to the adjacent group to form a ring; R4 and R5 each are a linear hydrocarbon group having from 1 to 6 carbon atom, and they may be the same or different, and may be bonded to the adjacent group to form a ring; and R6 and R7 each are a linear alkyl group having 1 or 2 carbon atoms, and they may be the same or different, and may be bonded to the adjacent group to form a ring.
Concretely, preferred examples of the organosilicon compound of formula (I) are neopentyl-n-propyldimethoxysilane, neopentyl-n-butyldimethoxysilane, neopentyl-n-pentyldimethoxysilane, neopentyl-n-hexyldimethoxysilane, neopentyl-n-heptyldimethoxysilane, isobutyl-n-propyldimethoxysilane, isobutyl-n-butyldimethoxysilane, isobutyl-n-pentyldimethoxysilane, isobutyl-n-hexyldimethoxysilane, isobutyl-n-heptyldimethoxysilane, 2-cyclohexylpropyl-n-propyldimethoxysilane, 2-cyclohexylbutyl-n-propyldimethoxysilane, 2-cyclohexylpentyl-n-propyldimethoxysilane, 2-cyclohexylhexyl-n-propyldimethoxysilane, 2-cyclohexylheptyl-n-propyldimethoxysilane, 2-cyclopentylpropyl-n-propyldimethoxysilane, 2-cyclopentylbutyl-n-propyldimethoxysilane, 2-cyclopentylpentyl-n-propyldimethoxysilane, 2-cyclopentylhexyl-n-propyldimethoxysilane, 2-cyclopentylheptyl-n-propyldimethoxysilane, isopentyl-n-propyldimethoxysilane, isopentyl-n-butyldimethoxysilane, isopentyl-n-pentyldimethoxysilane, isopentyl-n-hexyldimethoxysilane, isopentyl-n-heptyldimethoxysilane, isopentylisobutyldimethoxysilane, isopentylneopentyldimethoxysilane, diisopentyldimethoxysilane, diisoheptyldimethoxysilane, diisohexyldimethoxysilane, etc. Especially preferred are neopentyl-n-propyldimethoxysilane, neopentyl-n-pentyldimethoxysilane, isopentylneopentyldimethoxysilane, diisopentyldimethoxysilane, diisoheptyldimethoxysilane, and diisohexyldimethoxysilane; and more preferred are neopentyl-n-pentyldimethoxysilane and diisopentyldimethoxysilane.
The organosilicon compounds of the invention can be produced in any desired manner. Some typical routes for producing them are mentioned below. 
In the production routes, the starting compounds [1] are available on the market, or can be obtained, for example, through known alkylation or halogenation. The compounds [1] may be processed for known Grignard reaction to form the organosilicon compounds of formula (I).
The olefin polymerization catalyst of the invention comprises (A) a solid catalyst component comprising titanium, magnesium and an electron donor compound, (B) an organoaluminium compound, and (C) the organosilicon compound of formula (I). The method of the invention for producing olefin polymers comprises polymerizing an olefin by the use of the olefin polymerization catalyst. If desired, the olefin polymerization catalyst of the invention may be held on a carrier, or may be prepared through prepolymerization.
The catalyst components, the method for preparing the catalyst, and the polymerization method are described below.
The solid catalyst component for olefin polymer production comprises titanium, magnesium and an electron donor compound, and is formed from (a) a titanium compound, (b) a magnesium compound, and (c) an electron donor compound, which are mentioned below.
(a) Titanium Compound:
The titanium compound for use herein is not specifically defined, but preferred are those of a general formula (II):
TiX1p(OR8)4xe2x88x92pxe2x80x83xe2x80x83(II).
In formula (II), X1 represents a halogen atom, preferably a chlorine or bromine atom, more preferably a chlorine atom. R8 represents a hydrocarbon group, which may be saturated or unsaturated, and may be linear, branched or cyclic. It may contain a hetero atom such as sulfur, nitrogen, oxygen, silicon or phosphorus atom. Preferably, R8 is a hydrocarbon group having from 1 to 10 carbon atoms, more preferably an alkyl, alkenyl, cycloalkenyl, aryl or aralkyl group, and even more preferably a linear or branched alkyl group. A plurality of xe2x80x94OR8""s, if any in formula (II), may be the same or different. Specific examples of R8 are methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-decyl, allyl, butenyl, cyclopentyl, cyclohexyl, cyclohexenyl, phenyl, tolyl, benzyl and phenethyl groups. xe2x80x98pxe2x80x99 is an integer falling between 0 and 4.
Specific examples of the titanium compound of formula (II) are tetraalkoxytitaniums such as tetramethoxytitanium, tetraethoxytitanium, tetra-n-propoxytitanium, tetraisopropoxytitanium, tetra-n-butoxytitanium, tetraisobutoxytitanium, tetracyclohexyloxytitanium, tetraphenoxytitanium; titanium tetrahalides such as titanium tetrachloride, titanium tetrabromide, titanium tetraiodide; alkoxytitanium trihalides such as methoxytitanium trichloride, ethoxytitanium trichloride, n-propoxytitanium trichloride, n-butoxytitanium trichloride, ethoxytitanium tribromide; dialkoxytitanium dihalides such as dimethoxytitanium dichloride, diethoxytitanium dichloride, diisopropoxytitanium dichloride, di-n-propoxytitanium dichloride, diethoxytitanium dibromide; trialkoxytitanium monohalides such as trimethoxytitanium chloride, triethoxytitanium chloride, triisopropoxytitanium chloride, tri-n-propoxytitanium chloride, tri-n-butoxytitanium chloride, etc. Of those, preferred are high-halogen titanium compounds, and especially preferred is titanium tetrachloride. One or more of these titanium compounds may be used herein either singly or as combined.
(b) Magnesium Compound:
The magnesium compound for use herein is not specifically defined, but preferred are those of a general formula (III):
MgR9R10xe2x80x83xe2x80x83(III).
In formula (III), R9 and R10 each represent a hydrocarbon group, OR11 (where R11 is a hydrocarbon group), or a halogen atom. The hydrocarbon group for R9 and R10 includes, for example, an alkyl group having from 1 to 12 carbon atoms, a cycloalkyl group, an aryl group or an aralkyl group; R11 in OR11 for these includes, for example, an alkyl group having from 1 to 12 carbon atoms, a cycloalkyl group, an aryl group or an aralkyl group; and the halogen atom for these includes chlorine, bromine, iodine and fluorine atoms. R9 and R10 may be the same or different.
Specific examples of the magnesium compound of formula (III) are alkylmagnesiums and arylmagnesiums such as dimethylmagnesium, diethylmagnesium, diisopropylmagnesium, dibutylmagnesium, dihexylmagnesium, dioctylmagnesium, ethylbutylmagnesium, diphenylmagnesium, dicyclohexylmagnesium, butyloctylmagnesium; alkoxymagnesiums and aryloxymagnesiums such as dimethoxymagnesium, diethoxymagnesium, dipropoxymagnesium, dibutoxymagnesium, dihexyloxymagnesium, dioctoxymagnesium, diphenoxymagnesium, dicyclohexyloxymagnesium; alkylmagnesium halides and arylmagnesium halides such as ethylmagnesium chloride, butylmagnesium chloride, hexylmagnesium chloride, isopropylmagnesium chloride, isobutylmagnesium chloride t-butylmagnesium chloride, phenylmagnesium bromide, benzylmagnesium chloride, ethylmagnesium bromide, butylmagnesium bromide, phenylmagnesium chloride, butylmagnesium iodide; alkoxymagnesium halides and aryloxymagnesium halides such as butoxymagnesium chloride, cyclohexyloxymagnesium chloride, phenoxymagnesium chloride, ethoxymagnesium bromide, butoxymagnesium bromide, ethoxymagnesium iodide; magnesium halides such as magnesium chloride, magnesium bromide, magnesium iodide, etc.
Of those magnesium compounds, preferred are magnesium halides, alkoxymagnesiums, alkylmagnesiums, and alkylmagnesium halides.
The magnesium compounds may be prepared from metal magnesium, or magnesium-containing compounds.
One example of the method for preparing them comprises contacting metal magnesium with a halogen and an alcohol. The halogen includes iodine, chlorine, bromine and fluorine. Of those, preferred is iodine. The alcohol includes methanol, ethanol, propanol, butanol, octanol, etc.
Another example comprises contacting a magnesium alkoxide of Mg(OR12)2 (where R12 represents a hydrocarbon group having from 1 to 20 carbon atoms) with a halide.
The halide includes silicon tetrachloride, silicon tetrabromide, tin tetrachloride, tin tetrabromide, hydrogen chloride, etc. Of those, preferred is silicon tetrachloride.
For R12, mentioned are an alkyl group such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, hexyl or octyl group; a cyclohexyl group; an alkenyl group such as allyl, propenyl or butenyl group; an aryl group such as phenyl, tolyl or xylyl group; and an aralkyl group such as phenethyl or 3-phenylpropyl group. Of those, especially preferred are alkyl groups having from 1 to 10 carbon atoms.
The magnesium compound may be held on a carrier of silica, alumina, polystyrene or the like. The magnesium compounds mentioned above may be used herein either singly or as combined. They may contain, if desired, any other element of halogens such as iodine, or silicon, aluminium, etc., and may contain an electron donor of alcohols, ethers, esters, etc.
(c) Electron Donor Compound:
The electron donor compound includes oxygen-containing electron donors, for example, alcohols, phenols, ketones, aldehydes, esters of organic acids or inorganic acids, ethers such as monoethers, diethers or polyethers; and nitrogen-containing electron donors such as ammonia, amines, nitriles, isocyanates. The organic acids include carboxylic acids, and concretely mentioned is malonic acid. Of those electron donor compounds, preferred are polycarboxylates, and more preferred are aromatic polycarboxylates. Even more preferred are aromatic dicarboxylates. Preferably, the organic group in the ester moiety of these esters is a linear, branched or cyclic aliphatic hydrocarbon residue.
For these, concretely mentioned are dialkyl esters of dicarboxylic acids such as phthalic acid, naphthalene-1,2-dicarboxylic acid, naphthalene-2,3-dicarboxylic acid, 5,6,7,8-tetrahydronaphthalene-1,2-dicarboxylic acid, 5,6,7,8-tetrahydronaphthalene-2,3-dicarboxylic acid, indane-4,5-dicarboxylic acid, indane-5,6-dicarboxylic acid, in which the alkyl groups may be any of methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, n-pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 1,1-dimethylpropyl, 1-methylpentyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 1-ethylbutyl, 2-ethylbutyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl, n-nonyl, 2-methylhexyl, 3-methylhexyl, 4-methylhexyl, 2-ethylhexyl, 3-ethylhexyl, 4-ethylhexyl, 2-methylpentyl, 3-methylpentyl, 2-ethylpentyl and 3-ethylpentyl groups. Of these, preferred are diphthalates. Preferably, the organic group in the ester moiety of these esters is a linear or branched aliphatic hydrocarbon residue having at least 4 carbon atoms.
Preferred examples of the esters are di-n-butyl phthalate, diisobutyl phthalate, di-n-heptyl phthalate and diethyl phthalate.
These compounds may be used herein either singly or as combined.
The organoaluminium compound (B) for use in the invention is not specifically defined, but preferred are those having any of alkyl groups, halogen atoms, hydrogen atoms and alkoxy groups, aluminoxanes, and their mixtures. Concretely, they include trialkylaluminiums such as trimethylaluminium, triethylaluminium, triisopropylaluminium, triisobutylaluminium, trioctylaluminium; dialkylaluminium monochlorides such as diethylaluminium monochloride, diisopropylaluminium monochloride, diisobutylaluminium monochloride, dioctylaluminium monochloride; alkylaluminium sesquihalides such as ethylaluminium sesquichloride; linear aluminoxanes such as methylaluminoxane, etc. Of those organoaluminium compounds, preferred are trialkylaluminiums with lower alkyl groups each having from 1 to 5 carbon atoms; and more preferred are trimethylaluminium, triethylaluminium, tripropylaluminium, and triisobutylaluminium. One or more of these organoaluminium compounds are usable herein either singly or as combined.
The catalyst of the invention for olefin polymer production contains the organosilicon compound of formula (I) for the component (C).
One or more such organosilicon compounds may be used herein either singly or as combined.
There is no specific limitation on the method of preparing the solid catalyst component (A). To prepare it, for example, the titanium compound (a), themagnesiumcompound (b), the electron donor compound (c) and optionallyahalide (d) such as silicon tetrachloride may be contacted in any desired manner.
Some methods for preparing it are known, including those described in Japanese Patent Laid-Open Nos. 43094/1978, 135102/1980, 135103/1980 and 18606/1981. For example, herein employable are (1) a method comprising grinding a magnesium compound or a complex of a magnesium compound and an electron donor compound, in the presence of an electron donor compound and optionally a grinding aid, followed by reacting it with a titanium compound; (2) a method comprising reacting a liquid magnesium compound of no reducibility with a liquid titanium compound in the presence of an electron donor compound to give a solid titanium complex; (3) a method comprising reacting the product obtained in (1) or (2) with a titanium compound; (4) a method comprising reacting the product obtained in (1) or (2) with an electron donor compound and a titanium compound; (5) a method comprising grinding a magnesium compound or a complex of a magnesium compound and an electron donor compound, in the presence of an electron donor compound, a titanium compound and optionally a grinding aid, followed by processing it with a halogen or halide.
Apart from these methods, the solid catalyst component (A) may also be prepared according to the methods described in Japanese Patent Laid-Open Nos. 166205/1981, 63309/1982, 190004/1982, 300407/1982 and 47003/1983. For example, one method described comprises contacting an alkoxymagnesium with an electron donor compound and a titanium compound.
Still another method employable herein for preparing the solid catalyst component comprises holding a magnesium compound such as that mentioned above on a carrier of, for example, an oxide of an element of Groups II to IV of the Periodic Table (e.g., silicon oxide, silicon magnesium) or a composite oxide containing at least one oxide of an element of Groups II to IV of the Periodic Table (e.g., silica-alumina), followed by contacting the resulting solid with an electron donor and a titanium compound in a solvent at a temperature falling between 0 and 200xc2x0 C., preferably between 10 and 150xc2x0 C., for 2 minutes to 24 hours. For its type, the carrier is not specifically defined, and may be any of inorganic oxide carriers or other inorganic or organic carriers. For morphology control, however, preferred are inorganic oxide carriers and other inorganic carriers.
Concretely, the inorganic oxide carriers include SiO2, Al2O3, MgO, ZrO2, TiO2, Fe2O3, B2O3, CaO, ZnO, BaO, ThO2 and their mixtures, such as silica-alumina, zeolite, ferrite, and grass fibers. Of those, especially preferred are SiO2 and Al2O3. The inorganic oxide carriers may contain minor carbonates, nitrates, sulfates, etc.
Except those mentioned above, the carriers may further include magnesium compounds of a general formula, MgR13xX2y, such as typically MgCl2 and Mg(OC2H5)2, and their complexes. In the formula, R13 represents an alkyl group having from 1 to 20 carbon atoms, an alkoxy group having from 1 to 20 carbon atoms, or an aryl group having from 6 to 20 carbon atoms; X2 represents a halogen atom, or an alkyl group having from 1 to 20 carbon atoms; x falls between 0 and 2, y falls between 0 and 2; and x+y=2. R13 ""s and also X2""s may be the same or different.
The organic carriers include polymers such as polystyrenes, styrene-divinylbenzene copolymers, polyethylenes, polypropylenes, substituted polystyrenes, polyarylates; and starch and carbon.
For the carrier for use in the invention, preferred are MgCl2, MgCl(OC2H5), Mg(OC2H5)2, SiO2, and Al2O3. The properties of the carrier will vary, depending on the type thereof and the method for producing it. In general, however, the mean particle size of the carrier falls between 1 and 300 xcexcm, preferably between 10 and 200 xcexcm, more preferably between 20 and 100 xcexcm. Too small carriers are unfavorable as increasing the fine powder in the polymer produced; but too large carriers are also unfavorable as increasing coarse particles in the polymer produced, thereby lowering the bulk density of the polymer and often clogging hoppers.
The specific surface area of the carrier may fall generally between 1 and 1000 m2/g, but preferably between 50 and 500 m2/g; and the pore volume thereof may fall generally between 0.1 and 5 cm3/g, but preferably between 0.3 and 3 cm3/g. When any of the specific surface area or the pore volume oversteps the defined range, the catalyst activity will lower. The specific surface area and the pore volume may be obtained from the volume of the nitrogen gas adsorbed by the carrier, according to the BET method (see J. Am. Chem. Soc., Vol. 60, p. 309, 1983). It is desirable that the carrier is baked generally at 150 to 1000xc2x0 C., preferably at 200 to 800xc2x0 C., before used herein. In view of its ability for better morphology control and of its applicability to processes of vapor-phase polymerization, the solid catalyst component is preferably held on the carrier.
The optional component (d), halide includes silicon tetrabromide, tin tetrachloride, tin tetrabromide and hydrogen chloride, in addition to silicon tetrachloride.
The amount of the titanium compound to be used in preparing the solid catalyst component may fall generally between 0.5 and 100 mols, but preferably between 1 and 50 mols, per mol of magnesium of the magnesium compound to be used for the component. The amount of the electron donor to be used may fall generally between 0.01 and 10 mols, but preferably between 0.05 and 0.15 mols, per mol of magnesium of the magnesium compound. A halide, silicon tetrachloride or the like may be added thereto. Adding such a halide can improve the catalyst activity and the stereospecificity of the polymer produced, and can reduce the amount of fine powder in the polymer. The amount of the halide to be added thereto may fall generally between 0.001 mol/mol-Mg and 100 mol/mol-Mg, but preferably between 0.005 mol/mol-Mg and 50 mol/mol-Mg, more preferably between 0.1 mol/mol-Mg and 1 mol/mol-Mg.
The temperature at which the compounds for the solid catalyst component are contacted with each other may fall generally between xe2x88x9220 and 200xc2x0 C., but preferably between 20 and 150xc2x0 C.; and the time for the contact may fall generally between 1 minute and 24 hours, but preferably between 10 minutes and 6 hours.
The order for their contact is not specifically defined. For example, the constituent ingredients may be contacted with each other in the presence of an inert solvent such as a hydrocarbon solvent; or they may be previously diluted with an inert solvent such as a hydrocarbon solvent, and then contacted with each other. The inert solvent includes, for example, aliphatic hydrocarbons such as n-pentane, isopentane, n-hexane, n-heptane, n-octane, isooctane; aromatic hydrocarbons such as benzene, toluene, xylene; and their mixtures.
Preferably, the titanium compound is contacted twice or more with the magnesium compound serving as a carrier, so that it can be well held on the magnesium compound.
The solid catalyst component thus prepared through the contact treatment as above may be washed with an inert solvent such as a hydrocarbon solvent. For the inert solvent, usable are those mentioned above. The solid catalyst component may be stored in dry, or may be stored in an inert solvent such as a hydrocarbon solvent.
The amount of the catalyst components to be used in the invention is not specifically defined. In general, however, the amount of the solid catalyst component (A) to be used may fall between 0.0005 and 1 mmol, in terms of the titanium atom therein, per liter of the reaction capacity. For the amount of the organoaluminium compound (B) to be used, the atomic ratio, aluminium/titanium may fall generally between 1 and 1000, but preferably between 10 and 500. If the atomic ratio oversteps the defined range, the catalyst activity will be low. For the amount of the organosilicon compound (C) to be used, the molar ratio, organosilicon compound (C)/organoaluminium compound (B) may fall generally between 0.02 and 2.0, but preferably between 0.05 and 1.0. If the molar ratio oversteps the defined range, the catalyst activity will also be low.
The olefin to be polymerized herein is not specifically defined, but preferred are xcex1-olefins of the following general formula (IV):
R14xe2x80x94CHxe2x95x90CH2xe2x80x83xe2x80x83(IV).
In formula (IV), R14 represents a hydrogen atom or a hydrocarbon group, and the hydrocarbon group may be saturated or unsaturated, and may be linear, branched or cyclic. Concretely, the xcex1-olefins include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 3-methyl-1-pentene, 4-methyl-1-pentene, vinylcyclohexane, styrene, p-methylstyrene, etc. One or more of these olefins may be used herein either singly or as combined.
Of the olefins mentioned above, especially preferred is propylene. For its polymerization mode, propylene may be homopolymerized or copolymerized with any other xcex1-olefin such as ethylene, 1-butene or 1-hexene. If desired, dienes such as butadiene, and any other olefins may be additionally used in producing olefin polymers.
In olefin polymerization in the invention, if desired, an olefin may be first prepolymerized and then finally polymerized. For example, an olefin is prepolymerized in the presence of a catalyst prepared by mixing the above-mentioned components (A) solid catalyst component, (B) organoaluminium compound and (C) organosilicon compound in a predetermined ratio, generally at a temperature falling between 1 and 100xc2x0 C. and under a pressure falling between normal pressure and 50 kg/cm2G or so, and then finally polymerized in the presence of the catalyst and the prepolymerized product. The degree of prepolymerization may fall generally between 0.01 g/g-catalyst and1000 g/g-catalyst, but preferably between 0.01 g/g-catalyst and 100 g/g-catalyst. The mode of final polymerization is not specifically defined, and may be any of solution polymerization, slurry polymerization, vapor-phase polymerization or bulk polymerization. Especially preferred is slurry polymerization. Any of batch polymerization and continuous polymerization may apply to the invention. If desired, two-stage polymerization in which the two stages are effected under different conditions, or block polymerization in which an additional xcex1-olefin such as ethylene, 1-butene or 1-hexene is block-polymerized in the second stage may also apply to the invention. Further, multi-stage polymerization may apply thereto.
Regarding the reaction condition for the method of the invention, the polymerization pressure is not specifically defined and may fall generally between atmospheric pressure and 80 kg/cm2G, but preferably between 2 and 50 kg/cm2G; the polymerization temperature may fall generally between 20 and 90xc2x0 C., but preferably between 40 and 90xc2x0 C. The polymerization time shall vary, depending on the type of the starting olefin and on the polymerization temperature, and could not be indiscriminately defined. In general, however, it may fall between 5 minutes and 20 hours, preferably between 10 minutes and 10 hours or so.
The molecular weight of the polymer to be produced can be controlled by adding a chain transfer agent to the polymerization system, preferably hydrogen thereto. If desired, an inert gas such as nitrogen or the like may be present in the polymerization system.
Regarding the catalyst components for use in the invention, the component (A), the component (B) and the component (C) may be previously blended in a pre-determined ratio so that they are contacted with each other, and immediately an olefin may be applied thereto to start its polymerization. Alternatively, after the catalyst components have been contacted with each other, the resulting catalyst may be ripened for 0.2 to 3 hours or so, and thereafter an olefin may be applied thereto and polymerized in the presence of the thus-ripened catalyst. If desired, the catalyst components may be previously suspended in an inert solvent or olefin, and then fed into the polymerization system.
In the invention, the post-treatment after polymerization may be effected in any ordinary manner. For example, in vapor-phase polymerization, the powdery polymer produced is taken out of the polymerization reactor, and then exposed to a nitrogen stream atmosphere so as to remove the non-reacted olefin from it. If desired, the polymer may be pelletized through an extruder. In this step, a small amount of water, an alcohol or the like may be added to the polymer so as to completely inactivate the catalyst. In bulk polymerization, the polymer produced is taken out of the polymerization reactor, then the non-reacted monomer is completely removed from it, and thereafter the polymer may be pelletized.
The invention is described concretely with reference to the following Examples, which, however, are not intended to restrict the scope of the invention. The intrinsic viscosity [xcex7], the stereospecificity [mmmm], Mw/Mn, and MI of the samples produced are obtained as follows:
(1) Intrinsic Viscosity [xcex7]:
Measured in tetralin at 135xc2x0 C.
(2) Stereospecificity [mmmm]:
A sample of the polymer to be analyzed is dissolved in 1,2,4-trichlorobenzene, and subjected to a proton complete decoupling method for 13C-NMR (using JEOLxe2x80x2 EX-400) at 130xc2x0 C. Based on the signals for the methyl group obtained in the method, the stereospecificity [mmmm] of the sample is determined. The isotactic pentad fraction [mmmm] referred to herein for polymer stereospecificity was proposed by A. Zambelli et al. in Macromolecules, 6, 925 (1973), and it indicates the isotactic fraction in the pentad units of a polypropylene molecular chain measured in 13C nuclear magnetic resonance spectrometry. For the attribution of the peaks seen in the 13C nuclear magnetic resonance spectrometry, referred to is the A. Zambelli et al""s proposal in Macromolecules, 3, 687(1975).
(3) Mw/Mn:
This is calculated from the data of gel permeation chromatography (GPC). Briefly, 240 xcexcl of a polymer solution (0.1 weight/volume %) in 1,2,4-trichlorobenzene (containing 300 ppm of BHT) is applied to a mixed polystyrene gel column (Toso""s GMH6HT), and passed through it at 145xc2x0 C. and at a flow rate of 1.0 ml/min. The fractions are detected with an IR detector at a wavelength of 3.41 xcexcm.
(4) MI (melt index):
Measured according to JIS K-7210 under JIS #14 Condition (load: 2.16 kgf, temperature: 230xc2x0 C.).